Homework help in R studio needed

[KingKhan248]

Stat Programming #homework
Hey all,
need some help with this homework problem.
I need to find the difference between 2 values in the same row, but two different columns, and then print different messages based on whether the difference is positive, negative, or 0.

I started by first creating a data frame :
df <- data.frame(patient = c(1 , 2 , 3 , 4 , 5 , 6, 7 , 8),
baseline=c(100,110,109,99,103,101,125,130),
follow_up = c(105, 100, 102, 105, 100, 97, 108, 120))

Then I created another column : df$difference <- df$baseline - df$follow_up

Now what I want to do is write code that would cycle through each element in the column I created, and print the appropriate text based on value with respect to 0.
How do I do this? Any help is greatly appreciated!

[siddharthprabhu]

Hi KingKhan248, welcome to RStudio Community.

Please read our Homework Policy and modify your post to comply with the guidelines.

As for your question, there is a hint provided in the third line. R has a function called ifelse(). Try using that. You can type ?ifelse in the console to check the function documentation (it also has examples).

[KingKhan248]

Hello and thank you for the reply.

I have modified the question and hopefully I am now following the guidelines specified in the Homework Policy.

I tried ifelse() but somehow my 8 element column came back with 10 different outputs.

ifelse((df$difference > 0), print("Recovered"), print("More treatment")
Also, the first entry is -5, which should return "More treatments", did so, but twice for some reason.

ifelse (df[1,4] > 0, print("Recovered"), print("More treatments") )
[1] "More treatments"
[1] "More treatments"

[siddharthprabhu]

You don't need the print() statements. Try ifelse(df$difference > 0, "Recovered", "More treatment").

[KingKhan248]

Thank you so much! Now how would I format this?

df$difference
[1] -5 10 7 -6 3 4 17 10
ifelse (df$difference > 0, "Recovered", "More treatments" )
[1] "More treatments" "Recovered" "Recovered" "More treatments"
[5] "Recovered" "Recovered" "Recovered" "Recovered"

This is what I'm currently getting, is there anyway to make it one line so that it is clear which difference is being referred to?

[siddharthprabhu]

You could add it as a column to your data frame.

[technocrat]

In outline, the clearest way to do this is with the dplyr::mutate function using an case_when function to create the result column

suppressPackageStartupMessages(library(dplyr))

df <- data.frame(patient   = c(1 , 2 , 3 , 4 , 5 , 6, 7 , 8),
                 baseline  = c(100,110,109,99,103,101,125,130),
                 follow_up = c(105, 100, 102, 105, 100, 97, 108, 120))

df %>% mutate(outcome = case_when(
                        follow_up <  baseline ~ "negative",
                        follow_up == baseline ~ "unchanged",
                        follow_up >  baseline ~ "positive"
                        )
            )
#>   patient baseline follow_up  outcome
#> 1       1      100       105 positive
#> 2       2      110       100 negative
#> 3       3      109       102 negative
#> 4       4       99       105 positive
#> 5       5      103       100 negative
#> 6       6      101        97 negative
#> 7       7      125       108 negative
#> 8       8      130       120 negative

^{Created on 2020-07-25 by the reprex package (v0.3.0)}

Try this also with nested ifelse logical tests for contrast. Take this not as an answer to the specific question but as a template for all problems involving creating a new variable based on a transformation of one or more other variables.

If there's a requirement to use base only just apply the same logic.